Chain slack adjustment mechanism for mail sortation systems

ABSTRACT

A mail sortation system includes a frame system, a conveyor carried by the frame system, a driven axle on one end of the conveyor, a pair of split idler axles, one idler axel on each side of the conveyor, a chain from each idler axel to the driven axel, and a chain slack adjustment mechanism. The idler axels are configured to rotate independently of each other. The chains are coupled to the conveyor, such that rotation of the driven axle causes the idler axles to rotate and the conveyor to translate. The chain slack adjustment mechanisms remove slack in each chain by increasing the distance between the driven axle and the idler axles.

1. TECHNICAL FIELD

The present application relates to sortation conveyor systems, inparticular, the chain tensioning on shoe sorter transports used in suchsortation conveyor systems for sorting mail, such as letters, flats,parcels, trays, and polybags along sorter conveyor systems in parcelsorting machines.

2. DESCRIPTION OF RELATED ART

Machines for automatically sorting items such as mail, parcels andtrays, into one of an array of selected bins, bags, tubs, cardboardcontainers, or compartments, are common. Typically, such sortingmachines have a feed mechanism that inducts articles one-at-a-time ontobelts and/or onto conveyors. Sensing components along the travel pathmonitor and track the movement of the articles. Belts and/or conveyorsfeed items onto a transport which has multiple slats, driven by chains,that transport each item down the sorter's length. When an item hasreached an identified discharge location, control electronics commanddiverting gate assemblies or other redirecting mechanisms to dischargethe item from the transport slats into a specific destinationcompartment or bin.

Conventional chain driven sortation systems use two chains spanningbetween a motor driven axle with chain sprockets on one end of themachine, and a second non-powered idler axle also with chain sprockets.These axels are usually solid and span across the full width of thetransport. The chains must remain in tension between the driven andidler axles for the sorter to safely carry the parcel transport slatsand otherwise function properly. The solid drive axle to solid idleraxle arrangement used in parallel chain driven systems, such as used inparcel sorting systems, significantly contributes to chain wear. Thistype of wear is due to typical uneven parcel weight loading on the chaindriven slats, which causes a diagonal torqueing action of the chainsagainst the sprockets. This twisting motion of the chains against thesprockets significantly aggravates chain wear, which in turn acceleratesthe need for chain length adjustment.

Due to such wear, along with normal wear and tear, the chains increasein length such that the chains must be manually shortened to eliminateexcessive chain slack by removing slats and chain links from the chainson both sides of the sorter. Manually shortening these chains is a verytime consuming process, which causes a loss of the sorter's productiontime and the associated loss of considerable item processing profits.Although great strides have been made in the area of chain drivensortation systems, significant shortcomings remain.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed a characteristic of the system of thepresent application is set forth herein. However, the system itself, aswell as a preferred mode of use, along with further objectives andadvantages thereof, will best be understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a perspective view of a conventional item sortation conveyorsystem.

FIG. 2 is a simplified perspective view of the item sortation conveyorsystem of FIG. 1.

FIG. 3 is a side view of the item sortation conveyor system of FIG. 1.

FIG. 4 is an enlarged perspective view of the idler axle and sprocketassembly of the item sortation conveyor system of FIG. 2.

FIG. 5 is a simplified perspective view of a mail sortation systemhaving a chain slack adjustment mechanism according to the preferredembodiment of the present application.

FIG. 6 is a side view of the mail sortation system of FIG. 5.

FIG. 7 is an enlarged perspective view of a split idler axle assembly ofthe mail sortation system of FIG. 5.

FIG. 8 is an exploded view of the chain slack adjustment mechanism ofFIG. 7.

FIG. 9 is an enlarged partial exploded detail view of certain componentsof the chain slack adjustment mechanism of FIG. 8.

FIG. 10 is another enlarged partial exploded detail view of certaincomponents of the chain slack adjustment mechanism of FIG. 8.

FIG. 11A is an enlarged side view of the chain slack adjustmentmechanism of the mail sortation system of FIG. 5.

FIGS. 11B and 11C are enlarged side views of the chain slack adjustmentmechanism of the mail sortation system of FIG. 5, in which certaincomponents have been shown with cross-hatched lines to illustrate themovement of the chain slack adjustment mechanism.

While the system of the present application is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the method to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, combinations, and alternativesfalling within the spirit and scope of the present application.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the chain slack adjustment mechanism formail sortation systems of the present application are described below.In the interest of clarity, not all features of an actual implementationare described in this specification. It will, of course, be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedeveloper's specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

Reference may be made herein to the spatial relationships betweenvarious components and to the spatial orientation of various aspects ofcomponents as the devices are depicted in the attached drawings.However, as will be recognized by those skilled in the art after acomplete reading of the present application, the devices, members,apparatuses, etc. described herein may be positioned in any desiredorientation. Thus, the use of terms such as “above,” “below,” “upper,”“lower,” or other like terms, to describe a spatial relationship betweenvarious components or to describe the spatial orientation of aspects ofsuch components should be understood to describe a relative relationshipbetween the components or a spatial orientation of aspects of suchcomponents, respectively, as the device described herein may be orientedin any desired direction.

Referring now to FIGS. 1-4 in the drawings, a conventional chain andslat sortation conveyor system 100 is shown. As shown in FIG. 1,sortation conveyor system 100 is logically divided into three parts—afront section 101, a middle section 103, and an end section 105. Alongitudinal conveyor 110 extends through each of sections 101, 103, and105. Front section 101 includes an idler axle 106 having chain sprockets107 and other related carrier assemblies. Middle section 103 includesmultiple discharge containers 115. End section 105 includes a chaindrive motor 109, a drive axle 112, drive chain sprockets 116, and one ormore separate exit conveyors 118 for items that do not get sorted.Conveyor 110 travels from left to right, as shown in FIGS. 1 and 2,between front section 101 and rear section 105. Conveyor 110 includesmultiple slats 111 that extend transversely across conveyor 110. Slats111 are configured to carry block-shaped shoes 117. Shoes 117 slidealong corresponding slats 111 and push items off of slats 111 and intodischarge containers 115 according to preprogrammed instructions from acontrol system 122. It will be appreciated that control system 122includes multiple sensors, controllers, actuators, etc. Chains 124located on both sides of conveyor 110 are driven by chain drive motor109, drive axle 112, and drive chain sprockets 116; and are guided by adrive chain return guide 126.

In operation, various items are received onto slats 111 of conveyor 110at first section 101. Then, the items traverse along the conveyor 110through middle section 103. Then, at the appropriate time, controlsystem 122 activates shoes 117 causing the items to be discharged intothe appropriate discharge containers 115.

As shown in FIGS. 2 and 3, chain slack accumulates at the bottom returnpath just below drive axle 112 at the rear of conveyor system 100. Theslack in chain 124 is guided by chain return guide 126. Excessive chainwear eventually requires both chains 124 to be replaced. Chains 124 arelarge, heavy, specially made for the application and are very expensivein chain cost, labor to replace them, and system down time productionlosses during replacement. Therefore, reducing chain wear becomes amajor cost avoidance issue for economical sorter operation.

Chain slack 203 at the rear module accumulates from chain wear. Chainreturn guide 126 directs the chain slack back into a chain returnchannel under conveyor 110. If chain slack 203 becomes excessive, chain124 and slats 111 could snag on chain return guide 126, causingcatastrophic damage to conveyor system 100. An excessive chain slacksensor is commonly provided at the apex of chain slack 203 to haltconveyor system 100 if the acceptable chain slack length is exceeded.When the chain slack is in excess of the acceptable length, chains 124must be split, slats and chain links removed, and the chains joined backtogether before sorter operation can continue.

Referring now specifically to FIG. 4 in the drawings, a partial close-upperspective view from inside front section 101 is illustrated. Thefollowing description pertains to one side of the idler axle assembly,with the other side being a mirror image. An axle carrier assembly 501mounts directly to a sorter frame 502 with mounting hardware 407. Idleraxle 212, an axle bearing 406, and idler gear 108 are mounted to axlecarrier assembly 410 with an axle-bearing hub 403. The axle and sprocketassemblies are free to rotate, being supported by bearings 406 in theaxle-bearing hub 403. The horizontal axle assembly centerline, withrelationship to the entire sorter, is shown by the indicated dashedplane 409.

Referring now to FIGS. 5-7 in the drawings, a mail sortation system 500having a chain slack adjustment mechanism 501 according to the presentapplication is illustrated. In system 500, there is no chain slack loop.This is accomplished by the chain slack being adjusted out of the systemby increasing the distance between idler axles 1211 (see FIG. 6) anddriven axle 1214, until no slack remains, by actuating chain slackadjustment mechanism 501. Chain slack adjustment mechanism 501 providesa method to adjust the chain slack out of the system. Chain slackadjustment assembly 501 also provides spring tension on idler axleassembly to absorb minor shocks to chains 520 due to the inertial forcescaused by the starting and stopping of conveyor system 500, and theplacement and subsequent removal of asymmetrically loaded heavy articleson slats 522.

In the conveyor systems of the present application, no chain slackreturn guides are required at the rear of the sorter, as the chain slackhas been eliminated. As is shown, the single shaft front idler axle 106of the prior-art conveyor 100 has been replaced by two short independent(stub) idler axles 1211, one on each side, with each stub idler axle1211 being coupled to and adjusted by chain slack adjustment mechanisms501. By incorporating independent stub idler axles 1211 as a part ofchain slack adjustment mechanism 501, chain wear is significantlyreduced, chain life is extended, and the need for chain lengthadjustments is reduced. This configuration improves chain dynamics,because each chain 520 may be independently adjusted and tensioned toprevent uneven chain wear caused by uneven side-to-side slat loadingduring normal sorter operation.

Another novel feature of chain slack adjustment mechanism 501 is that byusing two separate independent stub idler axles 1211, chains 520 arefree to accommodate the unequal torque forces generated due to unevenitem weight distribution across slats 522 down the length of conveyorsystem 500. Chain slack adjustment mechanisms 501 may be selectivelymoved towards the front end of sortation system 500 to provideadjustment of chain slack, by increasing the distance between the stubidler axles 1211 and drive axle 1214. An idler gear 1207 is attached toeach stub idler axle 1211 and rotates therewith. Each stub idler axle1211 is supported by an axle bearing 1406, which is retained by an axlebearing hub 1403, each of which in turn is mounted to an idler axlecarrier assembly 1501. Each idler axle carrier assembly 1501 isconfigured to slide front-to-back inside a captured channel having alongitudinal slot for receiving guide pins 1703 from idler axle assembly1501. By using two stub idler axles 1211, the left and right sideconveyor chains 520 are decoupled. This allows the left and right sidechains 520 to skew relative to each other in reaction to typicaldifferential loading across conveyor slats 522. This resulting chainskewing action is absorbed by the chain slack adjustment springs 1616and the idler axle carrier slide assembly 1603 (see FIG. 8). Bypreventing the common chain binding caused with the prior-art design, asignificant reduction in chain wear results, dramatically increasing thetime before a system shutdown is required for slat and chain linkremoval, reducing costly sorter down time.

Referring now also to FIG. 8 in the drawings, an exploded perspectiveview of chain slack adjustment mechanism 501 is illustrated. A slideassembly 1603 is shown captured by retaining slide rails 1605. One outerstub idler axle 1211 and an axle-bearing hub 1403 are mounted to movableslide assembly 1603. Stub idler axle 1211 passes through adjustmentslide assembly 1603 to mount to idler gear 1207 and an inside axlebearing 1607 and an inner axle bearing hub 1403. Inner axle bearing hub1403 is mounted to sliding idler axle assembly 1501, which is retainedby guide pins 1703 (see FIG. 9) captured by guides mounted to the insideof conveyor frame 1503 (see FIG. 7). An adjustment rod assembly 1611 isfastened to an adjustment slide 1620 using a bulkhead plate 1617 (seeFIG. 9). Adjustment rod assembly 1611 includes bulkhead plate 1617, aspring 1616 with end caps 1618, and an adjusting nut 1622.

Referring now also to FIG. 9 in the drawings, certain moving componentsof chain slack adjustment mechanism 501 are illustrated. All componentsshown in FIG. 9 move toward the left when adjusting nut 1622 onadjustment rod assembly 1611 is tightened. Adjustment rod assembly 1611is fastened to chain slack adjusting slide assembly at the bulkheadplate 1617. An adjusting slide assembly 1603 is coupled to sliding idleraxle carrier assembly 1501. Sliding inner axle support assembly 1501 ismaintained level in a back-to-front orientation by guide pins 1703riding inside pin retainers 1503 (see FIG. 7). Stub idler axle 1211passes through and is supported by outer bearing 1607, which is capturedby outer bearing hub 1405. Stub idler axle 1211 also passes throughinner bearing 1406, which is captured and supported by inner axlebearing hub 1403.

Referring now also to FIG. 10 in the drawings, a slide assemblyadjustable stop 1901 is illustrated. Adjustable stop 1901 preventsexcessive rearward travel of slide assembly 1603 (see FIG. 8).Adjustable stop 1901 is preferably a threaded adjustment bolt 1911having a knurled end cap 1903. Adjustable stop 1901 threads into anadjustable stop bracket 1905. Adjustment bolt 1911 is screwed in or outof a threaded portion of bracket 1905, as required for optimumpositioning. A lock screw 1907 threads into a threaded nut 1909 onbracket 1905 to lock adjustment bolt 1627 into the desired position.

Referring now also to FIGS. 11A-11C in the drawings, the operation ofchain slack adjustment mechanism 501 is illustrated. Covers 1601 coverbracket chain slack adjustment mechanism 501 for personnel protectionfrom the moving chains. Idler axle bearing retainer assembly 1405 ismounted to and moves with the adjustment slide assembly 1603 in aback-to-front direction. Adjustment slide assembly 1603 is captured andguided by channeled guide rails 1605 mounted above and below adjustmentslide assembly 1603. Channeled guide rails 1605 keep adjustment slideassembly 1603 flush to the sorter frame and allow adjustment slideassembly 1603 to only move in a back-to-front direction. Bulkhead plate1617 is fastened to channeled guide rails 1605 to provide a framemounted surface that adjustment slide assembly 1603 can be pulledforward using threaded pull rod assembly 1611 with tension spring 1616,end caps 1618, and adjustment nut 1622. If the chain slack exceeds thetension range of tension spring 1616, tension spring 1616 will moveadjusting nut end cap 1618 to move away from bulkhead plate 1617,thereby triggering a position sensor 1623 that signals a control systemprogrammable logic controller (PLC) that a chain slack adjustment isneeded. A ruler 1627 can be included as a guide referencing theadjustment nut end cap position to view the relative amount ofaccumulated chain length increase since the last chain slack adjustment.

Slide assembly 1603 is mounted between two retaining rails 1605, whichpermits slide assembly 1603 to move left-to-right as shown in thefigures. Idler gear 1207, stub idler axle 1211, and inner and outer axlebearings are all mounted to and move with slide assembly 1603.Adjustment rod 1611 and spring assembly 1616 are adjusted to compressspring assembly 1616 against the stationary bulkhead 1617 to pull slideassembly 1603 to the left. By pulling slide assembly 1603 to the left,stub idler axle 1211 and idler gear 1207 are also pulled to the left,thereby creating tension on chain 520 to remove any accumulated chainslack (see FIG. 5). If the chain slack eventually becomes excessivecausing tension rod assembly 1611 to shift towards the left, sensor 1623signals an indication to the control system that spring tension assembly1616 requires adjustment. Slide assembly stop rod 1627 is adjustable tolimit the rearward travel of slide assembly 1627. Thus, chain slackadjustment mechanism requires minimal maintenance, even for continuousduty operation with heavy parcel loads; automatically notifies thecontrol system when adjustment is required; removes the highlytroublesome chain slack accumulation at the rear motor driven end; andsignificantly reduces long-term chain wear and elongation resulting insignificant operational savings due to reduced down time and maintenancecosts.

Although chain slack adjustment mechanism 501 is preferably driven bythe force of tension spring 1616, it will be appreciated that chainslack adjustment mechanism 501 may be driven and/or powered by othermeans, such as pneumatic, hydraulic, and/or electromagnetic systems.Such alternative systems may be controlled by the control system.

In FIGS. 11B and 11C, slide assembly 1603 of chain slack adjustmentmechanism 501 has been shown in cross-hatched lines to show the movementof slide assembly 1603 due to chain wear. The shaded slide is pulledtowards the left by tightening the adjustment nut, compressing thetension spring and added tension against the chain. By pulling slideassembly 1603 towards the left, the distance between drive axle 1214 andstub idler axles 1211 is increased, thereby removing the chain slack.The compressed spring 1616 provides tension on slide assembly 1603 toallow for moderate chain wear before manual chain slack adjustment isrequired by tightening the adjusting nut. The manual chain slackadjustment can be made while the conveyor system 500 is running,eliminating the need to do a time consuming and costly sorter shutdown.

Although the foregoing embodiments refer to removing the slack from thechains in chain-driven mail sortation systems, it will be appreciatedthat the slack removal mechanisms of the present application may also beused to remove the slack from belts in belt-driven mail sortationsystems.

The particular embodiments disclosed above are illustrative only, as theapplication may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered, combined, and/or modified,and all such variations are considered within the scope and spirit ofthe application. Accordingly, the protection sought herein is as setforth in the claims below. It is apparent that a system with significantadvantages has been described and illustrated. Although the system ofthe present application is shown in a limited number of forms, it is notlimited to just these forms but is amenable to various changes andmodifications without departing from the spirit thereof.

I claim:
 1. A mail sortation system, comprising: a frame system; aconveyor carried by the frame system; a driven axle on one end of theconveyor, the driven axle having driven axle chain sprockets on eachside of the conveyor; a pair of split idler axles, one idler axel oneach side of the conveyor, the idler axles being on an opposite end ofthe conveyor from the driven axle, each idler axle having idler axelchain sprockets, the idler axels being configured to rotateindependently of each other; a chain on each side of the conveyor, eachchain being coupled to the conveyor, each chain passing over a drivenaxel chain sprocket and a corresponding idler axel chain sprocket, suchthat rotation of the driven axle causes the idler axles to rotate andthe conveyor to translate; and a chain slack adjustment mechanism forremoving slack in each chain, each chain slack adjustment mechanismbeing coupled to the frame system and being adjustably coupled to acorresponding idler axle; wherein the slack in each chain is removed bythe chain slack adjustment mechanism by increasing the distance betweenthe driven axle and the idler axles; and wherein a single adjustmentbolt attached to a spring is used to adjust the distance.
 2. The mailsortation system of claim 1, wherein the chain slack adjustmentmechanism is adjusted in a sliding fashion.
 3. The mail sortation systemof claim 1, wherein the distance between the driven axle and the idleraxles is manually adjusted by actuating the chain slack adjustmentmechanism manually.
 4. The mail sortation system of claim 1, wherein thedistance between the driven axle and the idler axles is adjusted by thechain slack adjustment mechanism automatically.
 5. The mail sortationsystem of claim 1, wherein the distance between the driven axle and theidler axles is adjusted by the chain slack adjustment mechanismautomatically while the mail sortation system is operating.
 6. The mailsortation system of claim 1, wherein the actuation of chain slackadjustment mechanism minimizes wear on the chains.
 7. The mail sortationsystem of claim 1, wherein each chain slack adjustment mechanismcomprises: at least one side rail coupled to the frame system; and aslide assembly slidingly coupled to the side rail, the slide assemblybeing coupled to one of the idler axles; wherein the idler axle slidesrelative to the frame system in response to movement of the slideassembly.
 8. The mail sortation system of claim 7, wherein each chainslack adjustment mechanism further comprises: an adjustable tensioningrod assembly mounted to the slide assembly and the side rail, such thatadjustment of the tensioning rod assembly causes the idler axle to sliderelative to the frame system.
 9. The mail sortation system of claim 8,wherein each chain slack adjustment mechanism further comprises: atension spring operably associated with the tensioning rod for movingthe tensioning rod in response to changes in the slack of the chain. 10.The mail sortation system of claim 8, wherein each chain slackadjustment mechanism further comprises: a position sensor configured totrigger a system alarm if the tensioning rod moves past a predeterminedposition.
 11. The mail sortation system of claim 8, wherein each chainslack adjustment mechanism further comprises: an end stop traveladjustment assembly for limiting the rearward travel of the slideassembly during abnormal conditions.
 12. The mail sortation system ofclaim 1, further comprising: a control system for controlling theoperation of the chain slack adjustment mechanism.
 13. A chain slackadjustment mechanism for adjusting slack in a chain of a mail sortationsystem having a frame, the chain slack adjustment mechanism comprising:at least one side rail coupled to the frame; a slide assembly slidinglycoupled to the side rail; a single adjustment bolt attached to a spring;and an idler axle coupled to the slide assembly; wherein the idler axleslides relative to the frame in response to movement of the slideassembly.
 14. The chain slack adjustment mechanism of claim 13, furthercomprising: an adjustable tensioning rod assembly mounted to the slideassembly and the side rail, such that adjustment of the tensioning rodassembly causes the idler axle to slide relative to the frame.
 15. Thechain slack adjustment mechanism of claim 14, further comprising: atension spring operably associated with the tensioning rod for movingthe tensioning rod in response to changes in the slack of the chain. 16.The chain slack adjustment mechanism of claim 14, further comprising: aposition sensor configured to trigger a system alarm if the tensioningrod moves past a predetermined position.
 17. The chain slack adjustmentmechanism of claim 13, further comprising: an end stop travel adjustmentassembly for limiting the rearward travel of the slide assembly duringabnormal conditions.
 18. The chain slack adjustment mechanism of claim13, further comprising: a control system for controlling the operationof the chain slack adjustment mechanism.
 19. A mail sortation system,comprising: a frame system; a conveyor carried by the frame system; adriven axle on one end of the conveyor, the driven axle having a drivenaxle belt pulley on each side of the conveyor; a pair of split idleraxles, one idler axel on each side of the conveyor, the idler axlesbeing on an opposite end of the conveyor from the driven axle, eachidler axle having an idler axel belt pulley, the idler axels beingconfigured to rotate independently of each other; a belt on each side ofthe conveyor, each belt being coupled to the conveyor, each belt passingover a driven axel belt pulley and a corresponding idler axel beltpulley, such that rotation of the driven axle causes the idler axles torotate and the conveyor to translate; and a belt slack adjustmentmechanism for removing slack in each belt, each belt slack adjustmentmechanism being coupled to the frame system and being adjustably coupledto a corresponding idler axle; wherein the slack in each belt is removedby the belt slack adjustment mechanism by increasing the distancebetween the driven axle and the idler axles; and wherein a singleadjustment bolt attached to a spring is used to adjust the distance. 20.The mail sortation system of claim 19, further comprising: an adjustabletensioning rod assembly coupled to each belt slack adjustment mechanism,such that adjustment of the tensioning rod assembly causes the idleraxle to slide relative to the frame system.